A telephone headset allowing hands-free communication by means of a mobile phone, for example, has been proposed. In particular, a wireless headset is provided using short-distance wireless communication technology such as Bluetooth™ technology. For example, Patent Document 1 discloses a headset comprising a casing with a generally flat surface, the casing including a main body section having a microphone section, a receiver section, a battery section and a wireless communication section, and a projecting portion projecting from the generally flat portion. An ear pad section of the receiver section is attached to a distal end portion of the projecting portion and placed in a cavity of a concha. Such an arrangement of the wireless headset results in a heavy device with numerous parts including the microphone section, receiver section, battery section and wireless communication section. With the headset disclosed in Patent Document 1, the ear pad section is engaged with an inner wall of a cavity of a concha of a tragus and an antitragus, which prevents the headset from easily falling off the auricle.    Patent Document 1: Japanese Utility Model Registration No. 3105934